CITRUS DISEASES. 8L 



A much more virulent condition commonly exists among lemon 

 seedlings in the nurseries. Here the spotting occurs in connection 

 with scab, and not uncommonlj^ reaches such proportions as to cause 

 complete defoliation, with a resulting setliack to the young trees. Ex- 

 cept for their greater extent, and tendency 1o irregularity, the spots 

 do not differ from those on other host species. The fungus involved 

 is apparently Colletotrichum gloeosporiodes, although careful cul- 

 tural studies may reveal it as another species, as has been the case 

 with the anthracnose of limes in Florida and California, or at least 

 as a distinct variety. 



A distinct type of leaf spotting, but probably due to the same 

 fungus, has been observed in several newly set groves. After a 

 se.'ison practically all traces of this form have disappeared. On 

 the older and lower leaves, small deep-brown spots occurred, few 

 to many, nearly circular, from two to seven or eight millimeters in 

 diameter, and with slightly raised, very definite red-brown margins. 

 It is thought that these spots were due to infection in the nurseries 

 from the overabundant fungus material present there, but that the 

 trees once they were removed to clean surroundings were able to 

 resist, and finally eliminate the fungus. 



Anthracnose of the fruit. 



On the fruit typical anthracnose spots are produced. These are 

 deep brown in color, generally sunken, and vary in size from minute 

 points to areas several inches across. Any part of the fruit may 

 be attacked. It is seldom that more than isolated cases will be 

 found in a given tree, and most of these can be traced to som<^ initial 

 cause, a bruise, insect bite, or similar injury. Trees suffering from 

 root rot, foot-rot. or other disease seriously impairing their health, 

 show a large percentage of anthracnosed fruit. Fruit become more 

 susceptilile with maturity. 



Surface infection, known as tear staining, is considered elsewlicre. 

 as is also the phase in wliich complete rotting occui's. 



Withertip. 



The most serious damage inflicted by this fnngns results from 

 attacks on twigs and branches, although here again it is difficnlt to 

 say how much of the loss is really to be charged to this fungus, and 

 how much to other agencies affecting the general health of the tree. 



In the virulent form there is a sudden withering of terminal 

 twigs, the leaves drop, and the wood dies back for varying distances. 



